Railroad rails must be installed and repaired by joining ends of the rails while they are in use or assembled for use in the field. The joining process results in a joint between the rails which has a high strength, can be adjusted metallurgically, will not crack and can be economically formed in a very short time. As a criteria for such welding process, the process must be performed in substantially less than 45 minutes or such process will cause a delay or rerouting of train traffic. Two processes are now used for joining the rails in the field. The first process is the thermite technique wherein the spaced rails are surrounded by an appropriate sand mold and steel is melted and poured into the mold to fill the gap between the spaced rails. As the molten metal solidifies, the rails are joined; however, this process, which is universally used, has a failure rate that has been reported to be as high as 75%. In addition, the rails must be melted by the molten steel poured into the gaps between the rails. This melting requirement is not consistently met and also contributes to the failure of the joints produced in the field by the thermite process. To drastically decrease the deficiencies of the universally used thermite process, wherein steel is cast into the gaps between the rails, the ends of the rails may be joined by a flash butt welding process where the ends of the rails are driven together by tremendously high forces while electricity is passed between the rails. This causes the ends of the rails to become molten and pressure welded together. This process drastically reduces the failure rate of the joint to less than 10%. However, the flash butt welding process is best performed on rails in a manufacturing facility where the rails are not fixed on ties and can be forced together by stationary hydraulic equipment. To overcome the disadvantage of the universally used thermite process, the flash butt welding process has been modified for use in the field. However, the time for the welding process is substantially higher than the thermite process, since the rails must be stretched during the hydraulic forcing step, which step requires disconnecting one or both of the rails from the ties. This manual procedure must be reversed after the welding process has occurred, which is extremely time consuming.
Flash butt welding of rails consumes a portion of the rails which causes difficulties after the welding process has been completed. Also, sections of rails may have to be spliced into the rail to provide the necessary rail material for the weld. In addition, it is deficient to transport the hydraulic equipment needed to create the tremendous pressure between the rails to remote locations as required in the field. The butt welding process also produces a flash around the periphery of the joined rails which must be sheared off and then ground to allow a smooth operation and also to prevent stress concentrations in the joint during use. Even though the flash butt welding process drastically reduces the rate of failure of the joints made in the field, the thermite process is still used because it can be done rapidly by merely putting a mold around the gap between the spaced rails. The process does not require large hydraulic equipment and is relatively inexpensive. The failure rate is addressed by again performing the thermite process when a joint has failed. In doing this, a large section of the rail must be cut and a new section of rail is inserted in the open area. Consequently, a failed thermite joint normally results in the need for two replacement thermite joints, with their propensity for failure. As can be seen, even though the thermite process is universally used, there is a substantial need for some process which will join the rails in the field, which process has a low failure rate, but has the advantages associated with the thermite process. This need has existed for many years. Arc welding processes have been tried periodically, such as electroslag, continuous arc welding and submerged arc welding and combinations thereof. None of these processes has been successful because they use impractically large equipment, take an unacceptably long time to weld and finish grind, and have not resulted in acceptable failure rates. The arc welding process, especially in the lower part of the gap between the rails, has been inconsistent. In addition, these prior attempts to use arc welding for joining the ends of spaced railroad rails were expensive, required complex equipment and demanded a substantial time to prepare for the welding process and actually performing the welding process. Such time is not available in field welding of rails.
The welding methods and systems disclosed in my aforementioned patents and application address the foregoing disadvantages and problems encountered in connection with prior art techniques and, basically, provide for the ends of steel rails to be joined by longitudinally spacing the rails from each other to define a gap extending laterally therebetween and having base, web and head portions, positioning a barrier plate in the base gap so as to provide electrical contact between the barrier plate and the two rails, and filling the base, web and head gaps with molten metal by the gas shielded electric arc welding process which is initiated by bringing a welding gun downwardly into the gap until the filler metal electrode contacts the barrier plate to create the starting arc. In particular in connection with the methods and systems disclosed in my aforementioned patent U.S. Pat. No. 5,773,779, the root pass is laid using the spray transfer arc welding process and by moving the electrode laterally across the gap while oscillating the electrode longitudinally during the lateral movement. The spray welding process advantageously allows high penetration and high heat in the large area at the base of the rails. After the root pass and the next several layers are applied using the spray transfer process, the power supply is switched to the pulsed arc welding process and additional passes are made to fill the remainder of the base gap again, by moving the electrode laterally of the gap while longitudinally oscillating the electrode. When the filling of the gap approaches the area of the lower end of the web gap, contoured copper shoes are used to enclose the web and head gaps, and the gap between the webs is filled by continuing the shielded gas welding process in the pulsed mode. Again, in filling the web gap, the electrode is moved laterally across the gap while being oscillated longitudinally so as to spread the molten metal against the shoes and the ends of the rails defining the web gap. In laying the successive beads in the web gap, the electrode is moved, successively, in laterally opposite directions along a single path which would be linear except for the oscillation of the electrode. With regard in particular to the filling of the head gap in accordance with the disclosure in my patent U.S. Pat. No. 5,773,779, the beads of filler material are laid in a manner which provides for weld reinforcement at the laterally opposite edges of the transition and central portions of the rail heads so as to optimize protection against vertical separation of the head from the web during subsequent use of the rails and the high forces which are imposed thereon by locomotives, railway cars or other vehicles moving thereacross and causing sinuous distortions in the rails and through the welded joints therebetween. More particularly in this respect, beads of filler material are continuously laid sequentially in laterally opposite directions and vertically above one another between the laterally outer edges of the transition, central and crown portions of the head with movement of the welding electrode delayed at the beginning of the laying of each bead in a manner which produces vertically successive beads extending in opposite directions relative to one another.